The Grenada gazette. (Grenada, Miss.) 1885-18??, 1887-04-02
ORIGIN OF COLD WAVES.
Where The Come From. and How They
Spread and Expand Themselves.

w n6ID 1NeV Noulp @hu 80"
Spread and Expand Themselves.
.'The temperature has fallen west Of
Michigan and north Of Missouri and
Kansas, with 3 decided cold wave com
ing from Manitoba, where the temper
ATTIRE is now forty degrees below zero
So reported the Government Weather
Bureau one day last winter. The "cold
wave" has been known as such only
since the signal service was established.
Before that time it was called the ''cold
SPELL" or about as frequently the "cold
snap When daily reports came to
be made from all parts Of the country.
it was found that currents Of cold air
moved with great regularity Of direc-
ton and force. No better word could
be found to describe them than that
which names the corresponding move
ments of water.
These cold waves affect every part Of
the country east of the Rocky mount
aims, and come at all seasons of the
year. We hear little of them in the
summer. because then Il fall Of twenty
or thirty degrees mca only an agree
able change; but in winter such a
change threatens great discomfort, if
not actual peril. The waves naturally
come from the north. They spread
toward the south and east, losing force
and intensity as they expand.
What causes cold waves? The warm
air over the ocean and the Gulf rises
because of its expansion and conse-
quent lightness, and this invites the
cold air in TO take its place. At times
when the pressure is unusually light
over the Gulf. the cold wave does not,
move eastward, but, hugging close to
the mountains. rushes down into Texas
with increasing impetuosity, and be-
comes what the people there call a
''norther.' Its effects are sometimes
felt strongly at Vera Cruz and Cam
peachy. ,
This circumstance that cold air comes
in to take the place Of air which has
become warmed by contact with the
earth or water, will make clear to lis
why it il that we never have hot waves
to correspond. The heated air is
lighter. and so it rises and flows north
ward by currents above the surface of
the earth. The heavier cold currents
along upon the surface. The
colder air lifts the warm air above us,
and envclops us at nee On the con-
trary, when the warm winds blow
against the cold air, being themselves
lighter, they are lifted from the
of the earth, and it is only by
degrees that they can drive the cold
away. This will be made still more
plain by reference to the currents in
the ocean; for the same laws govern
the movements Of the air and of the
water. because the force which gives
them motion is one and the same;
namely, gravitation. If heat did not
the particles of air and of wa.
ter, and thus make them lighter. there
be a dead calm all the time on
and and sea.
The currents of the ocean have been
studied much more thoroughly than the
Winds. 1t is known that strong ocean
currents come down from Baffin's bay,
the shores of Labrador and New
oundland. These currents are of icy
'oldness. When they get a little below
newfoundland. they come upon the
iulf Stream, running almost directly
,cross their path. What now takes
'lace? Do they empty into the Gull
as IL river empties into an
'thcr on the land? Nothing of the
Kind. The cold water from the Arctic
ga is heavier than the warm water
the Gull. Accordingly, the cold
current, when it approaches the Cult
sinks beneath the surface,
'rosses the stream, and does not inter-
ere with the course of the warmer
Icebergs, however, can not
luck under. and are carried along by
he Gulf Stream until they are melted.
+ we could examine the bottom Of the
'cean about Newfoundland. we should
ind immense basins, like the beds of
great lakes, scooped out Of the de-
of sand and gravel which con
titute 'the Banks" They have been
made by the colder of two streams
whose paths have crossed.
The cold waves from Manitoba leave
ew marks Of their passage upon the
urface of the earth, No permanent
ecord remains Of their course, but tel
communication discloses the
act that in The atmosphere, as in the